1. Technical Field of the Invention
The present invention relates generally to surveillance systems, and specifically to event detection using images captured by surveillance systems.
2. Description of Related Art
Surveillance systems commonly employ video cameras to monitor facilities. Historically, these cameras have transmitted analog video images of an area under surveillance to a security monitoring center for inspection and storage. In many facilities, analog video cameras are being replaced with digital cameras that detect and capture still images of events, such as the appearance of an intruder, a malfunction, or a fire within the area under surveillance. Digital cameras provide several advantages over analog video cameras. For example, digital cameras can be radio linked and battery powered to eliminate the need for the costly fixed infrastructure of video cables and power lines, making surveillance systems cheaper and easier to deploy.
However, digital cameras have limited sensitivity, and in areas of low illumination or at night, a source of artificial illumination is required. In commercial applications, lights can be left on at night in order to illuminate the facilities that must be secured. However, in residential applications, lights that are left on at night can be disturbing to both the occupants of a property and their neighbors. In addition, if a illumination source is attached to a battery-powered camera, constant illumination would reduce the life of the battery, necessitating frequent battery replacements. Therefore, what is needed is a surveillance system capable of operating under low illumination conditions.